1. Field of the Invention
The present invention relates to a liquid crystal display element in which a liquid crystal layer is interposed between a pair of substrates laminated to each other by a sealing material such that alignment films are opposed to each other with a predetermined gap between the alignment films, and a projection type liquid crystal display device using the liquid crystal display element.
2. Description of the Related Art
A projection type liquid crystal display device such as a liquid crystal projector or the like separates light emitted from a light source into red, green, and blue, modulates the pieces of color light by three light valves each formed by a liquid crystal display element (hereinafter referred to as an LCD), synthesizes color luminous fluxes after the modulation, and then enlarges and projects resulting light onto a projection surface.
As the light valves included in the liquid crystal projector or the like, an LCD of an active matrix driving type based on thin film transistor (hereinafter referred to as TFT) driving is generally used.
A display system of the active matrix driving type includes a twisted nematic (TN type) liquid crystal having a molecular alignment twisted by 90 degrees.
Recently, for higher luminance, higher contrast, higher definition, and longer life of liquid crystal projector devices, a vertical alignment type liquid crystal element has begun to be considered.
A vertically aligned liquid crystal material is a liquid crystal material having a negative dielectric anisotropy (a negative value obtained by subtracting a dielectric constant ∈ε in a direction perpendicular to the major axis of a liquid crystal molecule from a dielectric constant ε= in a direction parallel to the major axis of the liquid crystal molecule). Liquid crystal molecules are aligned in a direction substantially perpendicular to the surface of a substrate when voltage applied to the liquid crystal is zero. Therefore this vertical alignment type liquid crystal display element can provide a very high contrast ratio.
The vertical alignment type liquid crystal display element is used as both a transmissive type and a reflective type, and is expected to become mainstream in the liquid crystal projector together with inorganic alignment films for longer life.
For uniform display by an LCD of the active matrix driving type, liquid crystal molecules need to be aligned uniformly over the entire surface of a substrate.
Two substrates each having an alignment film and an electrode formed thereon are arranged such that the alignment films of the respective substrates are opposed to each other, and are laminated to each other by a sealing material in a sealing region situated around a pixel display region where an image is actually displayed.
In order to control a gap between the substrates, a pillar spacer formed by a resist has recently been used.
An empty cell is manufactured by undergoing these processes. Thereafter a liquid crystal is filled into the empty cell, whereby a liquid crystal cell is manufactured.
Incidentally, the above-described liquid crystal is formed of a few kinds of simple-substance liquid crystal materials, and is thus referred to also as a liquid crystal composition. A liquid crystal display element is manufactured by attaching polarizing plates to the manufactured liquid crystal cell.
Various liquid crystal display elements, including materials, have been proposed. For more information, this specification uses Japanese Patent Laid-open No. 2005-306949 as patent Document 1, Japanese Patent Laid-open No. 2003-119248 as Patent Document 2, Japanese Patent Laid-open No. 2003-119249 as Patent Document 3, Japanese Patent Laid-open No. 2006-22228 as Patent Document 4, and Japanese Patent Laid-open No. 2001-255562 as Patent Document 5.